填空题 A a member of the National Academy of Science
B a pseudo-scientist
C a science popularizer
D a reporter
E an astronomer
F a physicist

填空题 In Sagan's opinion, Velikovsky might be ______.

填空题 With Cosmos and others, Sagan enjoyed his fame as ______.

填空题 From the passage, we may conclude that the author of the passage may be ______.

填空题 From the description we know that Sagan was ______.